Natural Gas Midstream
Emission Inventories from Natural Gas Storage Facilities using Regional Frequency Comb Laser Monitoring and Aircraft Flyovers Last Reviewed August 2017

DE-FE0029168

Goal
The University of Colorado at Boulder, in collaboration with University of California at Davis, Scientific Aviation, and the National Institute of Standards and Technology (NIST) will quantify emissions from natural gas storage facilities and provide an emissions estimate for the Environmental Protection Agency’s (EPA's) Greenhouse Gas Inventory (GHGI). The measurements collected to inform emission estimates include ground-based regional-scale measurements at a variety of storage facilities for extended periods (continuous measurements over multiple months) each using a unique laser technology with minute time resolution and sensitivity to leaks down to 0.1 kg hr-1, together with broad ranging aircraft measurements at those and additional facilities. The campaign will achieve 1) continuous capture of diurnal to seasonal variability of emissions from entire facilities with component-level resolution (e.g. specific compressor, sealed well head, etc. emissions rates), 2) complementary and wide-spread aircraft surveys to assess and characterize the mean seasonal total emissions rates of many different facilities, and 3) combination of the detailed ground based and aircraft measurement data with Large Eddy Simulation transport models for determining emission inventories and reducing uncertainties. The integration of these independent yet highly complementary datasets will provide, for the first time, quantification of the mean state and temporal variability (diurnal to annual) of emissions from natural gas storage.

Performer
University of Colorado, Boulder, CO 80309
University of California, Davis, CA 95616
Scientific Aviation, Boulder, CO 80301
National Institute of Standards and Technology, Boulder, CO 80305; Gaithersburg, MD 20899

Background
Very few research studies have concentrated specifically on quantifying methane emissions from underground natural gas storage wells and fields, which can involve complex infrastructure spread over hundreds or thousands of acres (5-10 square miles). The vast underground gas reservoirs may be connected to dozens of surface access points, for example old well heads in the case of a depleted reservoir field. Each is capable of leaking methane, as are the arrangements of handling equipment and compressor stations located on site. The EPA’s GHGI includes an estimate for underground natural gas storage, but that estimate is limited in scope and based on emissions from compressors. Amidst a climate of increasing scientific and public interest in quantifying the amount of methane lost to the atmosphere along the natural gas supply chain, the storage sector has quickly become recognized as a critically under-studied component. In addition, new state and federal safety regulations for the storage sector are already in process following the recent Aliso Canyon blowout event. An understanding of emissions from this sector will be critical for informed policymaking.

Impact
The project provides a highly cost-effective method for quantifying the entire cross-industry spectrum of underground natural gas storage wells and fields. From a scientific standpoint, this research fills an important gap in knowledge of the midstream natural gas supply chain – the storage sector. The comprehensive nature of the study, covering all important aspects of emissions quantification (total emissions across many fields, time history and variability, and uncertainty analysis), will create a complete emissions inventory for the sector. Furthermore, the project will have long-term benefits for the environmental impacts of the natural gas storage system by providing important information about leak rates and frequencies, and specific high-risk components in use in the storage sector to operators and policymakers. Finally, this approach is a more cost and resource efficient means to quantify methane emissions from underground storage facilities than is currently available, and may represent a new paradigm for emissions studies in other sectors with regional footprints.

Accomplishments (most recent listed first)
The preparation and development of the micrometeorological instrument package, as well as preparation of a low-rate (~1 Hz) horizontal wind speed measurement instrument that can be used to infer micrometeorological parameters, has been completed.

Current Status (August 2017)
Preparation for site modeling and configuration of the ground-based system are proceeding as planned. Initial large eddy simulation (LES) model runs have been completed at 2 to 10 m resolution for the McDonald Island site using historical meteorological data collected during October to November 2016. Detailed facility-level information has been obtained for the McDonald Island site, so that inclusion of all potential emission sources is incorporated into the models. The team has formalized plans for a site visit on July 20, 2017. At this site visit, optimal beam configurations will be finalized for ground deployment. The ground deployment and flights at McDonald Island will begin in August.

Additional site modeling has been initiated for the Aliso Canyon and Honor Rancho storage facilities for the dual purposes of 1) comparison of modeled atmospheric conditions with existing aircraft data, and 2) assessment of suitability for possible future deployments at those sites.

Project Start: October 1, 2016
Project End: September 30, 2019

DOE Contribution: $1,323,130
Performer Contribution: $330,773

Contact Information
NETL – Eric Smistad (eric.smistad@netl.doe.gov or 281-494-2619)
University of Colorado Boulder – Greg Rieker (greg.rieker@colorado.edu or 303-492-6802)